Choose the incorrect sentence regarding an electrostatic precipitator.

• A
  The electrostatic precipitator can remove over $99$ percent of particulate matter present in the exhaust from a thermal power plant.
• B
  It has electrode wires that are maintained at several thousand volts.
• C
  The collecting plates are grounded and attract the charged dust particles.
• D
  The velocity of air between the plates must be high enough to allow the dust to fall.